From 5cf29cea9368d10ffe4c2dc1c00390c40003c462 Mon Sep 17 00:00:00 2001
From: serge-sans-paille <serge.guelton@telecom-bretagne.eu>
Date: Sun, 5 Jun 2022 11:06:07 +0200
Subject: [PATCH] Add support for casting nullptr in _Py_CAST_impl

Fix #93442
---
 Include/pyport.h         | 17 +++++++++++++++++
 Lib/test/_testcppext.cpp |  8 ++++++++
 2 files changed, 25 insertions(+)

diff --git a/Include/pyport.h b/Include/pyport.h
index 6ea2bba232b3dd..fedcdb401c0513 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -27,6 +27,22 @@
 #  define _Py_STATIC_CAST(type, expr) static_cast<type>(expr)
 extern "C++" {
     namespace {
+
+        // Overloads to cope with NULL and nullptr
+        template <typename type>
+        inline type _Py_CAST_impl(long int ptr) {
+            return reinterpret_cast<type>(ptr);
+        }
+        template <typename type>
+        inline type _Py_CAST_impl(int ptr) {
+            return reinterpret_cast<type>(ptr);
+        }
+        template <typename type>
+        inline type _Py_CAST_impl(std::nullptr_t) {
+            return static_cast<type>(nullptr);
+        }
+
+        // Overloads to cope with regular pointers
         template <typename type, typename expr_type>
             inline type _Py_CAST_impl(expr_type *expr) {
                 return reinterpret_cast<type>(expr);
@@ -37,6 +53,7 @@ extern "C++" {
                 return reinterpret_cast<type>(const_cast<expr_type *>(expr));
             }
 
+        // Overloads to cope with object that defines a conversion to `type`
         template <typename type, typename expr_type>
             inline type _Py_CAST_impl(expr_type &expr) {
                 return static_cast<type>(expr);
diff --git a/Lib/test/_testcppext.cpp b/Lib/test/_testcppext.cpp
index eade7ccdaaff7a..f2eee00d04a599 100644
--- a/Lib/test/_testcppext.cpp
+++ b/Lib/test/_testcppext.cpp
@@ -74,6 +74,14 @@ test_api_casts(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
     Py_INCREF(strong_ref);
     Py_DECREF(strong_ref);
 
+    // gh-93442: handle null pointer variants.
+    Py_INCREF(nullptr);
+    Py_DECREF(nullptr);
+    Py_INCREF(NULL);
+    Py_DECREF(NULL);
+    Py_INCREF(0);
+    Py_DECREF(0);
+
     Py_DECREF(obj);
     Py_RETURN_NONE;
 }